A good first start would be for the Attorney General of the United States to appoint a Special Counsel to investigate and prosecute any crimes associated with the false framing of the Trump Campaign leading to the unnecessary investigation based on demonstrably false information such as Christopher Steele’s Trump–Russia dossier that was likely created by Russian intelligence to undermine Donald Trump. The new Special Prosecutor can also investigate where Hillary Clinton as well as Barack Obama and leading members of his administration fit into potentially creating a tool to undermine the incoming U.S. administration.
Either Rudy Giuliani, as a former Associate Attorney General of the United States and former United States Attorney for the Southern District of New York, or Chris Christie, as a former U.S. Attorney for the District of New Jersey and former Governor of New Jersey, would be a great choice for this appointment.
I reckon that the Special Counsel would likely wrap up his investigation and be in mid of some prosecutions by mid to late 2020.